Hydraulic system



Nov. 30, 1965 J. R. MCGUIRE 3,220,318

HYDRAULIC SYSTEM Filed Nov. 2l, 1963 2 Sheets-Sheet 1 JOHN R. Mo Gu/RE BY 1||| lll MEII Nov. 30, 1965 J. R. MCGUIRE HYDRAULIC SYSTEM 2 Sheets-Sheet 2 Filed NOV. 2l, 1963 m mm mw United States Patent O 3,220,318 HYDRAULIC SYSTEM `lohn R. McGuire, 141 Enid Lane, Northfield, lll. Filed Nov. 21, 1963, Ser. No. 325,369 11 Claims. (Cl. 91-461) This invention relates to hydraulic systems and, more particularly, to hydraulic systems which are particularly well adapted for moving work loads.

The primary object of the present invention is to afford a novel hydraulic system for lifting, lowering, and otherwise moving workloads.

Another object is to afford a novel hydraulic system for raising and lowering loads, such as, for example, for raising and lowering articulated booms on fire trucks, utility trucks, repair trucks, and the like.

Hydraulic systems for raising and lowering loads, such as, for example, for raising and lowering such articulated booms and the like, have heretofore been known in the art. However, such systems as have been heretofore known in the art have commonly had several inherent disadvantages, such as, for example, not being adapted for effective remote control; being diflicult, if not impossible, to operate in such a manner as to consistently smoothly raise and lower a load; not being effective to hold a load stationary at any and all points along its path of travel; being large and cumbersome in size; being impractical and ineffective in operation; or being difficult and expensive to produce commercially, and the like. It is an important object of the present invention to overcome such disadvantages.

Another object is to afford a novel hydraulic system of the aforementioned type which is operable to effectively control movement of a work load in a novel and expeditious manner.

Another object is to afford a novel hydraulic system of the aforementioned type wherein the parts thereof are so constituted and arranged as to enable remote control of the system to be effected in a novel and expeditious manner.

Yet another object of the present invention is to enable control of the operation of hydraulic control valves to be effected in a novel and expeditious manner.

. An object ancillary to the foregoing is to obtain throttling or feathering of such control valves in a novel and expeditious manner by the actuation of pilot valves.

Another object is to enable the rate of movement, and the acceleration and deceleration of work loads being moved to be controlled in a novel and expeditious manner.

A further object of the present invention is to prevent unintentional sudden movements of work loads being moved by hydraulically operated units.

Another object is to afford a novel hydraulic system of the aforementioned type which is practical and efficient in operation, and which may be readily and economically produced commercially.

Other and further objects of the present invention will be apparent from the following description and claims and are illustrated in the accompanying drawings which, by way of illustration, show a preferred embodiment of the present invention and the principles thereof and what I now consider to be the best mode in which I have contemplated applying these principles. Other embodiments of the invention embodying the same or equivalent principles may be used and structural changes may be made as desired by those skilled in the art without departing from the present invention and the purview of the appended claims.

In the drawings:

FIG. 1 is a partially schematic View of a hydraulic ice system embodying the principles of the present invention;

FIG. 2 is a fragmentary view of the hydraulic systern shown in FIG. l, with certain parts thereof disposed in different operative position; and

FIG. 3 is a View similar to FIG. 2, with certain parts disposed in different operative position.

A hydraulic system 1, embodying the principles of the present invention, is shown in vthe drawings to illustrate the presently preferred embodiment of the present invention.

The hydraulic system 1 includes, in general, a' hydraulically operated control unit 2 for moving, or controlling the movement of, a work load; a suitable source of working fluid, such as a hydraulic pump 3, for actuating the control unit 2; a directional control valve 4 for controlling the actuation of the control unit 2; and a pilot valve 5 for remotely controlling the actuation of the control valve 4, FIG. l.

The control unit 2 shown in the drawings includes an elongated cylinder 6 having a piston 7 reciprocably mounted therein. The piston 7 has an enlarged head 8 on one end thereof slidably mounted in the cylinder 6, and an elongated shank or connecting rod 9 extending from the head 8 and projecting outwardly through one end 10 of the cylinder 6. The free end of the connecting rod 9 of the piston 7 may be suitably connected to a work load, not shown, for moving the latter. The control unit 2 is shown in the drawings in such position that the cylinder 6 and the piston 7 extend in a horizontal direction. However, it will be appreciated by those skilled in the art that this is merely by way of illustration, and not by way of limitation, and that the control unit 2 may be disposed in any position desired for moving the work load.

The piston head 8 is reciprocable between the end portion 10 and the end portion 11 of the cylinder 6, to thereby effect longitudinal reciprocation of the connecting rod 9 into and out of the cylinder 6. In the position shown in the drawings, the piston 7 may be directly connected to a work load for effecting horizontal movement of the latter, or by suitable actuating mechanism, such as, for example, a boom, or the like, not shown, may be connected to a work load for raising and lowering the same in a manner well known in the art.

The directional control valve 4 includes an elongated, substantially cylindrical-shaped housing 12 having an elongated bore 13 extending longitudinally therethrough, the bore 13 being closed at its respective opposite ends by end walls 14 and 15 of the housing 12. Five annular grooves or recesses 16, 17, 18, 19, and 20 are formed in the housing 12 and are spaced from each other axially thereof, the recesses 16-20 projecting radially outwardly from the bore 13 and opening radially inwardly thereinto. An inlet port 21 extends radially through the side wall of the housing 12 into direct communication with the centermost recess 18; two combination inlet and outlet ports 22 and 23 extend through the side wall of the housing 12 into direct communication with the recesses 17 and 19, which are disposed on opposite sides of the central recess 18; and two outlet ports 24 and 25 extend through the side wall of the housing 12 into direct communication with the recesses 16 and 20, respectively, which are disposed outwardly of, and on opposite sides of the recesses 17 and 18, for a purpose which will be discussed in greater detail presently.

The pump 3 may be any type of suitable hydraulic pump readily available on the market. The inlet side of the pump 3 is connected by a suitable inlet conduit 26 to a suitable source of hydraulic fluid, such as a sump 27, and the outlet side thereof is connected by a suitable outlet conduit 28 to the inlet port 21 of the directional control valve 4 for feeding working uid, under pressure, to the control valve 4.

The two outlet ports 22 and 23 of the control valve 4 i are connected by suitable conduits 29 and 3i), respectively, to ports 31 and 32, respectively, in the end portions 10 and 11, respectively, of the cylinder 6, so that the hydraulic fluid may be fed by the pump 3 through the outlet ports 22 and 23 of the control valve 4 to respectiveends of the cylinder 6, as will be discussed in greater detail presently. The other outlet ports 24 and 25 of the control valve 4 are connected by respective branches 33 and 34 of a bifurcated conduit 35, the other end of which is connected to the sump 27.

p The conduit 35 affords ya return conduit for feeding working fluid from the valve 4 back to the sump 27. A back pressure valve 36, which may be in the form of a check valve which opens in a direction to enable flow through the conduit 35 from the control valve 4 to the sump 27, is embodied in the conduit 35 to insure that a minimum back pressure is maintained on the valve 4 during operation 'of the hydraulic system 1.

The control valve 4 also includes an elongated spool 37 slidably mounted in the bore 13 in the housing 12 for longitudinal reciprocation therein. The spool 37 includes two lands 38 and 39 on respective ends thereof, and another land 40 disposed on the intermediate portion thereof midway between the lands 38 and 39. The lands 38-40 are complementary in outside transverse cross-section to the transverse cross-section of the bore 13, and are slidably mounted in the bore 13 with a snug, but freely slidable fit effective to prevent leakage of hydraulic fluid axially of t-he bore 13 past the lands 38-40. The radial outward projection of the lands 38-40 relative to the main body portion 37 affords radially outwardly opening recesses 41 and 42 -disposed between the lands 38 and 40, and the lands 39 and 40, respectively, for a purpose which will be discussed in greater det-ail presently.

Each of the lands 38-40 has a radially outwardly opening annular recess 43, 44, and 45 formed in the outer (periphery thereof, respectively, and the spool 37 is hollow between the end lands 38 and 39 to afford a passageway 46 which interconnects the recesses 43-45. The lands 38-40 are disposed in such position on the spool 37 that when the spool 37 is disposed in longitudinally centered position in the housing 12, as shown in FIG. 1, the recess 45 on the land 40 is disposed in radially aligned communication with the inlet recess 18 in the housing 12, and the recesses 43 and 44 on the outermost lands 38 and 39,

respectively, are disposed in radially aligned communication with the outlet recesses 16 and 20, respectively. The lands 38-40 of the spool 37 are also so disposed relative ,to each other, that when the spool 37 is disposed in the aforementioned longitudinally centered position in the housing 12, the outlet recesses 17 and 19 in the housing 12 are disposed in radially aligned communication with the longitudinal central portions of the recesses 41 and 42, respectively, in the spool 37. With this construction, when the spool 37 is disposed longitudinally centered position in the housing 12, and working fluid is being fed by the pump 3 through the conduit 28 into the inlet port 21 of the control valve 4, the working uid may ow from the inlet port 21 through the inlet recess 18, the groove 45, the passageway 46, the grooves 43 and 44, the outlet recesses 16 and 20, the outlet ports 24 and 25, and the conduit back to the sump 27. At this same time, the outlet ports 22 and 23 of the valve 4 are sealed from the inlet port 21 by the land 40, and from the outlet ports 24 and 25 by the lands 38 and 39, respectively, so that there is no flow of hydraulic fluid through the control valve 4 into or out of the control unit 2.

The spool 37 is somewhat shorter in length than the bore 13 of the control valve 4, and two compression coil springs 47 and 48 are mounted in the bore 13 between the end walls 14 and 15 and the respective adjacent ends of the spool 37. The coil springs 47 and 48 are of such type, and are so disposed in the housing 12 that they at all times yieldingly urge the spool 37 toward centered position in the housing 12.

The pilot valve 5, like the control valve 4, includes an elongated substantially cylindrical-shaped housing 49 having a longitudinally extending b-ore 50. The pilot valve housing 49 also has a centrally located annular inlet recess 51, two combination inlet and outlet recesses 52 and 53 disposed on opposite sides of the inlet recess 51, and two other outlet recesses 54 and 55 disposed on opposite sides of the recesses 52 and 53, FIG. l. The inlet recess 51 is connected by a suitable conduit 56 to the out-let end of a pressure-compensated flow-control valve 57. The inlet end of the flow-control valve 57 is connected by a suitable conduit 58 to the outlet conduit 28 connected to the pump 3. Another conduit 59, having a pressure limiting valve 60 therein, is connected between the conduit 56 and the sump 27. The pressure limiting valve 60 is so constructed that it will open to permit flow from the conduit 56 to the sump 27 when the pressure in the conduit 56 is above a predetermined pressure. A system relief valve 61 is mounted in a conduit 62 which extends from the conduit 28 to the sump 27. The conduit 62 is connected to the conduit 28 between t-he pump 3 an-d the conduit 56, and the relief valve 61 is adapted to open when the pressure in the conduit 28 exceeds a predetermined pressure to thereby atford a safety valve for venting the entire hyldraulic system 1 to sump prior to the development of excessive pressures therein.

An actuator 63 is loperatively connected to the spool 37 of the directional control valve 4 for actuating, and controlling the position of, the spool 37 for a purpose which will be discussed in greater detail presently. The actuator 63 includes an elongated cylinder 64, which is closed at the respective opposite ends thereof by end walls 65 and 66, respectively. The cylinder 64 has two ports 66 and 67 therethrough adjacent the end walls 65 and 66, respectively, for feeding working fluid into and out of the cylinder 64. A piston 68 having an enlarged head 69 and -an elongated shank or connecting rod is reciprocahly mounted in the cylinder 64 in such position that the head 69 may reciprocate longitudinally of the cylinder 64 between the ports 66 an-d 67.

The shank 70 of the piston 68 extends from the head 69 outwardly through the end wall 66 of the cylinder 64, and extends through the end wall 14 of the housing 12 of the control valve 4 into engagement with the adjacent end of the spool 37. The shank 70 is operatively connected to the spool 37 in such position that reciprocation of the piston 68 in the cylinder 64 is effective to correspondingly longitudinally reciprocate the spool 37 in the control valve 4.

The housing 49 of the pilot valve S has two ports 71 and 72 extending radially therethrough into communication with the recesses 52 and 53, respectively. The ports 71 and 72 are operatively connected by conduits 73 and 74 to the ports 67 and 66, respectively, in the cylinder 74 `of the actuator 63. Also, the housing 49 of the pilot valve 5 has two ports 75 and 76 extending radially therethrough into communication with the recesses 54 and 55, respectively, and the ports 75 and 76 are connected to the branches 77 and 78 of a bifurcated conduit 79, the other end of which conduit is connected to the sump 27 An elongated spool 80 is mounted in the bore 50 of the housing 59 of the lpilot valve 5, for longitudinal reciprocation therein. The spool 80 includes two radially outwardly projecting lands 8 1 and 82 disposed at the respective opposite ends thereof, and another land 83 disposed at the longitudinal central portion thereof, midway between the lands 81 and 82. The lands 81 and 82 are spaced from the central land 83 to afford recesses 84 and 85, respectively, therebetween. Both ends 86 and 87 of the land 83 taper inwardly from the central body portion thereof, and the inner ends 88 and 89 of the lands 81 and 82, respectively, similarly taper radially inwardly from the main body portions thereof, for a purpose which will be discussed in greater detail presently.

The spool 80 is considerably shorter than the bore 50 of the housing 49, and two compression coil springs 90 and 91 are mounted in the bore 56 between the end walls 92 and 93 of the housing 49 and the respective adjacent ends of the spool 80, respectively. The springs 90 and 91 are of such construction, and are so disposed in the housing 49 that they yieldingly urge the spool 80 toward longitudinally centered position in the bore 5t) of the pilot valve 5 in all positions of the spool 80.

An elongated rod 94 is attached to the end of the spool 80 on which the land 81 is disposed, and projects outwardly therefrom, in axial alignment therewith, through the end wall 92 of the housing 49. A bell crank lever 95, having a short leg 96 and a longer leg 97 is pivotally mounted by a suitable pin 98 to a mounting bracket 99 projecting outwardly from the housing 49 of the pilot valve 5. The pin 98 extends through the junction of the leg 96 and 97, and the end portion of the leg 96 is operatively connected to the outer end portion of the rod 94 by a suitable pin and slot connection 100. The leg 97 of the bell crank-lever 95 affords a handle by which the bell crank lever 95 may be oscillated manually, or otherwise, on the pin 98 to thereby correspondingly reciprocate the spool 80 in the housing 49 of the pilot valve 5.

The lands 81-83 are of such size that they t in the Vbore 50 of the housing 49 with a snug but freely slidable t so as to prevent leakage of hydraulic fluid therepast. The lands 81-83 are so disposed relative to each other that when the spool 80 is disposed in longitudinally centered position, as shown in FIG. 1, the land 83 is disposed in -covering relation to the inlet recess 51 to thereby close the latter and prevent flow of working fluid into the bore 50 from the conduit 56; the recesses 52 and 54 in the housing 49 are disposed in direct communication with the recess 84 in the spool 80; and the recesses 53 and 55 in the housing 49 are disposed in direct communication with the recess 85 in the spool 80. With this construction, both ends of the cylinder 64 of the actuator 63 are vented to the sump 27, when the spool 80 lis disposed in longitudinally centeredV position in the housing 49, so that, with the bell crank lever disposed in neutral position, the pilot valve 5 is ineffective to hold the piston 68 against the urging of either of the springs 47 and 48 and the latter are effective to -center the spool 37 As will be discussed in greater detail presently, by oscillating the bell crank lever 95 between the positions shown in FIGS. 2 and 3, the position of the spool 37 in the control valve 4 may be controlled to thereby control the direction of actuation, actuation of the control unit 2.

As will be appreciated by those skilled in the art, the hydraulic system 1 may operate under various pressure conditions, ranging all the way from a relatively few pounds of pressure to several thousand pounds of pressure. However, the novel hydraulic system 1 is particularly well adapted for use in operations wherein the maximum pressure desired to have available for actuating the control unit 2 is relatively high, such as, for example, 1500 pounds per square inch, but it is desired to operate the pilot valve 5 at relatively low pressures such as, for example, 100 pounds per square inch. Under such conditions, the directional control valve 4 is relatively large in size, but even under such conditions, the size of the pilot valve 5 may be relatively small.

For operation under the aforementioned conditions, a hydraulic system 1 embodying the principles ofthe present invention may be so constructed that, for example, the system relief valve 61 will open when the pressure in the conduit 62 is 1500 pounds; the pressure limiting valve 60 will open when the pressure in the conduit 59 exceeds 100 pounds; the back pressure valve 36 will open when the pressure in the conduit 35 exceeds 100 pounds; the pressure compensated control valve 57 is set to maintain the flow of working Huid therethrough at a constant rate of one gallon per minute irrespective of the pressure thereon; and the maximum rate of flow of working fluid through the conduit 28 is fifty gallons per minute. Under these conditions, the maximum pressure to which the pilot valve 5 is subjected is limited to approximately one hundred pounds per square inch, the pressure limiting valve 60 affording a relief valve for feeding the conduit 56 to the sump 27 when the pressure in the conduit 56 exceeds one hundred pounds per square inch; but the maximum pressure to which the directional control valve 4 may be subjected is approximately 1500 pounds per square inch, the pressure at which the system relief valve 61 will open. Under these conditions, pilot valve 5 may be considerably smaller in size than the control valve 4, while still affording Very sensitive, accurate control of the control unit 2 by actuation of the pilot valve S.

In the operation of the hydraulic system 1 shown in the drawings, when the bell crank lever 95 is disposed in the position shown in FIG. 1, the system is in neutral, the inlet recess 51 of the pilot valve 5 being closed by the spool 80, and both sides of the cylinder 64 of the actuator 63 being vented through the pilot valve 5 to the sump 27, so that the springs 47 and 48 in the control valve 4 are effective to center the spool 37. With the spool 37 disposed in centered position, both sides of the cylinder 6 of the control unit 2 are closed by the spool 37 from communication with the pressure conduit 28 and the return conduit 35 so that the piston 7 .is held stationary in the cylinder 6.

When it is desired to extend the piston 7, that is, to move it to the right, as viewed in FIG. 1, the bell crank lever 95 may be rotated in a clockwise direction, as viewed in FIG, l, from the position shown in FIG. 1 toward the position shown in FIG. 2. Such movement of the bell crank lever 95 is effective to move the spool 80 of the pilot valve 5 to the left, as viewed in FIG. 1. As the spool moves to the left, toward the fully actuated position, shown in FIG. 2, the land 82 is effective to progressively close the recess 55, and the land 83 is effective to progressively open the recess 51. The opening of the recess 51 permits working uid to flow from the pump 3 through the conduit 28, the conduit 58, the pressure cornpensated ow control valve 57, the conduit 56, and the recess 51 into the recess 85 between the lands 82 and 83 on the spools 80 of the pilot valve 5. With the spool 80 in such position, the uid may ow from the recess 85 through the recess 55 and the conduit 79 back to sump 27, and, also, may flow from the recess 85 through the recess 53 and the cond-uit 74 into the left side of the cylinder 64 of the actuator 63. At the same time, during such movement of the spool 80, the connection between the recess 52 and the recess 54 through the recess 84 remains open so that uid in the cylinder 64 of the actuator 63 to the right of the piston head 69 may fiow therefrom through the conduit 73, the recess 52, the recess 84, the recess 54, and the conduit 79 back to the su-mp 27. Therefore, the pressure of the working iluid owing into the left end of the actuator cylinder 64 is effective to urge the piston 68 to move to the right and thus actuate the control valve 4.

The lands 81-83 are so disposed on the spool 80 of the pilot valve 5 that as the spool 80 thus moves to the left toward the actuated position shown in FIG. 2, the recess 51 is progressively opened by movement of the end portion 87 of the land 83 thereacross; the recess 52 is progressively restricted by the movement of the end portion 86 of the land 83 thereacross; and the recess 55 is progressively restricted by the movement of the end portion 89 of the land 82 thereacross. This affords a sensitive throttling effect, the movement of the land 83 affording a gradual increase in the ow of working fluid into the recess 85 in the pilot valve 5, and the movement of the land 82 affording a gradual increase of the percentage of fluid owing from the recess 85 through the recess 53 to the left end of the actuator cylinder 63 instead of through the recess 55 to the sump 27; but the movement of the land 83 also affording a gradual decrease in the ow of fluid from the right end of the cylinder 64 through the recess 52 to thereby create somewhat of a build up of back pressure on the right side of the piston 68.

This construction and mode of operation of the pilot valve affords an elective pilot valve by which the extent of movement and rate of movement of the piston 68 of the actuator 63 may be readily and accurately controlled without the occurrence of unintentional sudden movements of the actuator piston 68. For example, when the spool 80 has moved to the left a suicient distance to rst crack open the connection between the recess 51 and the recess 85, the connection between the recess 55 and the recess 85 is relatively large, and the pressure between the recess 55 and the sump 27 being relatively small, the major portion of the working iluid flowing inwardly through the recess 51 tends to ow through the recess 55 back to the sump 27. As the movement of the spool 80 to the left progresses, the recess 55 is progressively restricted so that a greater portion of the working uid flowing inwardly through the recess 51 tends to flow through the conduit 74 to the left end of the cylinder 64 to thereby accelerate the movement of the piston 68 to the right, as viewed in FIG. 1, caused by the flow of working uid into the cylinder 64 to the left of the piston head 69. However, preferably, at no time during the movement of the spool 80 to the left, as viewed in FIG. 2, is the land 82 effective to completely close the recess 55, as this tends to prevent any sudden surge of pressure on the left end of the piston 68. Furthermore, the progressive, partial closing of the recess 52, and the consequent build-up of partial back pressure on the piston 68 further tends to prevent any sudden surge of acceleration of the movement of the piston 68 to the right, as viewed in FIG. 1.

Thus, it will be seen that the rate of movement of the piston 68 to the right, as viewed in FIG. 1, may be carefully controlled by the proper movement of the bell crank lever 95 between the position shown in FIG. 1 and the position shown in FIG. 2. In addition, by moving the bell crank lever 95 to the proper position, the spool 37 in the control valve 4 may be moved to a desired corresponding position and held there indeiinitely. For example, if the spool 80 in the pilot valve 5 is moved to the left to a partially opened position, most of the fluid ow through the pilot valve 5 is from the inlet thereof through the return conduit 79 to the sump 27, and the pressure applied to the left side of the piston 68 by working fluid owing through the conduit 64 and the port 66 is limited to a predetermined amount, the ow of working fluid through the ow control valve 57 remaining at a constant rate. Such increase in pressure in the cylinder 64 of the actuator 63 is effective to move the piston 68 to the right, and, therefore, move the spool 37 of the control valve 4 to the right. Movement of the spool 37 to the right decreases the pressure of the spring 47 thereon, and increases the pressure of the spring 48 thereon, and the movement of the spool 37 to the right is limited to that position wherein the pressure of the spring 48 is effective to balance the combined pressure of the spring 47 on the spool 37 and the pressure of the working fluid on the left side of the cylinder head 69.

The aforementioned movement of the spool 37 to the right is effective to progressively move the grooves 43-45 in the lands 38-40 out of communication with the recesses 16, 18, and 20 in the control valve 4. This movement ot' the grooves 43-45 is effective to progressively close off the ow of working fluid from the conduit 28 through the valve 4 and back through the conduit 35 to the sump 27. At the same time, this movement of the spool 37 to the right, is effective to progressively open the communication between the recess 18 in the housing 12 of the control valve 4, and the recess 41 in the spool 37 to thereby progressively increase the flow of working Huid from the pump 3 through the conduit 28, the recess 18 of the control valve 4, the recess 17, the conduit 29 and the piston 32 into the left side of the cylinder 6 to thereby move the piston 7 to the right, as viewed in FIG. 1. Also, the aforementioned movement of the spool 37 to the right is effective to move the land 39 progressively out of covering relation to the outlet recess 28 to thereby progressively open the outlet recess 25 of the control valve 4 and thereby permit an increase in ow of Working iluid to sump 27 from the right end of the cylinder 6. Thus, increased movement of the spool 37 from the neutral position shown in FIG. 1 toward the fully extended position shown in FIG. 2 increases the speed of movement of the piston 7 to the right, as viewed in FIG. 2, assuming that the load on the piston 7 remains constant.

When the piston 7 reaches its extreme extended position, as shown in FIG. 2, with the valve 4 in fully opened position, as shown in FIG. 2, the full pressure capacity of the hydraulic system 1 is exerted on the left end of the piston 7 to hold the latter in the fully extended position. If, for reasons of safety, or the like, it is desired to maintain this full pressure on the piston 7, the bell crank lever 95 may be retained in actuated position, as shown in FIG. 2. However, if it is desired to merely lock the piston 7 in fully extended position, the bell crank lever 95 of the pilot valve 5 may be returned to neutral position, as shown in FIG. 1. The resulting movement of the spool to neutral position again opens both ends of the .actuator cylinder 64 to sump 27 to thereby permit the spring 48 to return the spool 37 of the control valve 4 to centered position and thereby close the conduits 29 and 30 to the respective ends of the cylinder 6 of the control unit 2, and thus lock the piston 7 in extended position.

The head 69 of the piston 68 in the actuator 63 preferably has a bleed opening, such as the opening .181 therein, FIGS. 1-3 so that when the spool 80 of the pilot valve 5 is disposed in centered position, working fluid may slowly pass through the piston head 69 and prevent drawing of a vacuum on either side thereof.

The pilot valve 5 and the control valve 4 are so constituted and arranged that retraction of the piston 7 of the control unit 2 to the left, as viewed in FIGS. 1-3 may be effected by moving the bell rcrank lever from the neutral position shown in FIG. 1 toward the actuated position shown in FIG. 3. This operation is identical to the operation hereinbefore described relative to the movement of the piston 7 to the right, except that it is reverse thereof, the spool 80 moving to the right in the pilot valve housing 49, to thereby reverse the flow of working lluid into and out of the cylinder 64 of the actuator 63, and thereby cause the piston 68 to move t0 the left, and thus move the spool 37 of the control valve 4 to the left, and reverse the flow of working fluid into and out of the cylinder 6 of the control unit 2. The control and throttling effected by the pilot valve 5 during such operation is the same as during the above-described extending operation, except that in the retracting operation the throttling is elfected by the lands 83 and 81, rather than the lands 83 and 82, the land 83 throttling the recesses 51 and 53, and the land 81 throttling the recess 54. Also, the operation of the control valve is the same, except that it is the reverse of the extending operation thereof, the lands 38-40 throttling the recesses 16, 20, and 18, respectively, by a movement thereof to the left rather than to the right.

With the back pressure valve 36 disposed in the conduit 35 it is insured that during movement of the piston 7 of the control unit 2 in either direction inthe cylinder 6, there will always be a back pressure thereon resisting such movement, when the control valve 4 is in fully open position. This insures that the movement of the piston 7 in either direction will never be under runaway conditions.

With the hydraulic system 1 constructed in accordance with the present invention, the pilot valve 5 affords a practical and efficient, sensitive control for controlling 9 the rate of actuation of the control valve 4 and of the control unit 2.

Also, the present invention affords a novel hydraulic system wherein the pilot valve 5 affords a practical and efficient control for accurately controlling the actuated position of the spool 37 in the control valve 4.

In addition, it will be seen that the present invention affords a novel and practical hydraulic system which is practical and efficient in operation and which may be readily and economically produced commercially.

Thus, while I have illustrated and described the preferred embodiment of my invention, it is to be understood that this is capable of variation and modification, and I therefore do not wish to be limited to the precise details set forth, but desire to avail myself of such changes and alterations as fall within the purview of the following claims.

I claim:

1. A hydraulic system comprising (a) a pilot valve,

(b) a source of working lluid under pressure,

(c) a constant rate of flow conduit means operatively connected to said source and to said pilot valve,

(d) control means,

(e) other conduit means for feeding said lluid from said source to said control means and back to said source,

(f) another valve in said other conduit means for controlling the ilow of said iluid through said other conduit means to said control means and back to said source,

(g) actuating means operatively connected to said pilot valve and controlled thereby for actuating said other Valve, and

(h) said pilot valve being actuatable to simultaneously progressively increase the amount of fluid ilowing to said actuating means and progressively decrease the amount of iluid flowing back to said source from said actuating means.

2. A hydraulic system comprising (a) a source of working uid,

(b) conduit means for feeding said working fluid from said source and then back to said source,

(c) a control unit,

(d) a control valve in said conduit means and operatively connected to said control unit,

(e) said control valve 1) having (a) one position wherein all of said fluid flowing through said conduit means flows back to said source, and (b') two other positions wherein at least a portion of said iluid flowing through said conduit means llows to said control unit for actuating the latter, and (2) being actuatable between said one position and said other positions to progressively vary the amount of said fluid flowing to said control unit and the amount of fluid ilowing back to said source,

(f) actuating means operatively connected to said control valve for actuating the latter,

(g) a constant rate of flow conduit means for feeding said fluid from said source,

(h) a pilot valve in said last-mentioned conduit means and operatively connected to said actuating means,

(i) said pilot valve (l) having (a) one position operable to close said lastmentioned conduit means, and (b') two other positions wherein a portion of said fluid flowing through said last-mentioned conduit means flows to said actuatl0 ing means and another portion flows back to said source, and

(2) being actuatable between said one position and said other positions to progressively increase the amount of lluid flowing to said actuating means and progressively decrease the amount of fluid flowing back to said source,

(j) and means for actuating said pilot valve.

3. A hydraulic system comprising (a) a pilot valve (b) a source of working fluid under pressure,

(c) a constant rate of flow conduit means operatively connected to said source and to said pilot valve,

(d) control means,

(e) other conduit means for feeding said fluid from said source to said control means and back to said source,

(f) another valve operatively connected to said control means for controlling the flow of said fluid from said other conduit means to said control means and back to said other conduit means,

(g) means in said other conduit means for maintaining lsubstantially constant pressure of the fluid being fed through said other conduit means from said source to said other valve,

(h) means operatively connected to said pilot valve for receiving fluid therethrough from said rst-mentioned conduit means for actuating said other valve,

(i) actuating means for said other valve, and

(j) said pilot valve being actuatable to simultaneously progressively increase the amount of fluid flowing to said actuating means and progressively decrease the amount of fluid flowing back to `said source from said actuating means.

4. A hydraulic system comprising (a) control means for controlling the movement of a Work load,

(b) a control valve for actuating said control means,

(c) said control Valve having (l) rst inlet means,

(2) rst outlet means,

(3) second outlet means, and

(4) means for selectively connecting said rst outlet means to said rst inlet means and said second outlet means,

(d) a source of pressurized working lluid (e) rst conduit means for feeding said working fluid from said source to said first inlet means,

(f) second conduit means for feeding said working lluid from said second outlet means to said control means for actuating the latter,

(g) third conduit means for feeding said working iluid from said third outlet means back to said source,

(h) means -in said third conduit means for maintaining a predetermined minimum pressure in said rst conduit means,

(i) actuating means operatively connected to said control valve for actuating the latter,

(j) a pilot valve for actuating said actuating means,

(k) said pilot valve having (l) second inlet means,

(2) third outlet means,

(3) fourth outlet means, and

(4) means for selectively connecting said third outlet means to said second inlet means and said fourth outlet means,

(5) said last named means selectively progressively 4opening said second inlet means and progressively closing said fourth outlet means,

(l) fourth conduit means for feeding said working lluid at a constant velocity from said source to said second inlet means,

(m) fifth conduit means for feeding said working iluid from said third outlet means to said actuating means, for actuating the latter, and

(n) sixth conduit means for feeding said working fluid from said fourth outlet means back to said source.

5. A hydraulic system comprising (a) control means for controlling the movement of a work load,

(b) a source of working fluid,

(c) a control valve for a-ctuating said control means,

(d) said control valve including (1) first inlet means operatively connected to said source for receiving said fluid from said source,

(2) first outlet means operatively connected to said control means for feeding said fluid between said first outlet means and said control means,

(3) second outlet means operatively connected to said source for feeding said fluid from said control valve to said source, and

(4) a control member movable into (a) one position effective to operatively connect said first inlet means to said second outlet means, and to close said first outlet means, and

(b') two other positions effective to operatively connect respective ones of two sides of said control means to said inlet means and the respective other of said two sides to said second outlet means,

(e) means operatively connected to said second outlet means, for maintaining a predetermined minimum back pressure at said second outlet means,

(f) -actuating means operatively connected to said control member for moving the latter into said positions,

(g) a pilot valve for controlling said actuating member,

(h) said pilot valve including (l) second inlet means operatively connected to said source for receiving said uid from said source,

(2) third outlet means for feeding said iiuid between said actuating means and said pilot Valve,

(3) fourth outlet means operatively connected to said source for feeding said fluid from said pilot valve to said source, and

(4) another control member movable into (a') one position effective to close said second inlet means and to operatively connect said third outlet means to said fourth outlet means, and

(b) two other positions effective to operatively connect respective ones of two sides of said actuating means to both said second inlet means and said third outlet means, and to operatively connect the respective other of Said two sides of Said actuating means to said fourth outlet means, and

(5) means actuatable to simultaneously progressively increase the rate of flow of fluid to said actuating means and progressively decrease the rate of flow of fluid therefrom back to said source,

(i) means, including said second inlet means, for feeding said fluid at a substantially constant rate of fiow from said source to said pilot valve when said other control member is disposed in either of said two other positions thereof.

6. A hydraulic system as defined in claim 5, and

(a) in which said first-mentioned control member has a passageway therethrough in position to connect 4said first inlet means to said second outlet means when said first control member is disposed in said one position thereof.

7. A hydraulic system as defined in claim 6, and

(a) in which said first-mentioned control member has (l) outwardly projecting spaced lands thereon,

and

(T2) outwardly opening recesses disposed between respective pairs of said lands, and

(b) in which said lands and said recesses are disposed in such position that when said first-mentioned control member is disposed in said two other positions thereof respective ones of said recesses connect respective portions of said first outlet means to said rst inlet means and said second outlet means, respectively.

8. A hydraulic system comprising (a) control means for controlling the movement of a work load,

(b) a source of working uid,

(c) a control valve for actuating said control means,

(d) said control valve including (1) first -inlet means operatively connected to said source for receiving said fluid from said source,

(2) first outlet means operatively connected to said control means for feeding said fluid between said first outlet means and said control means,

(3) second outlet means operatively connected to said source for feeding said fluid from said control valve to said-source, and

(4) a control member movable into (a) one position effective to operatively connect said first inlet means to said second outlet means, and to close said first outlet means, and

(b) two other positionseffective to operatively connect respective ones of two sides of said control means to said first inlet means and the respective other of said two sides to said second outlet means,

(e) means operatively connected to said second outlet means, for maintaining a predetermined minimum back pressure at said .second outlet means,

(f) actuating means operatively connected to said control member for moving the latter into said positions,

(g) a pilot valve for controlling said actuating member,

(h) said pilot valve including (1) second inlet means operatively connected to said source for receiving said fluid from said source,

(2) third outlet means for feeding said fluid between said actuating means and said pilot valve,

(3) fourth outlet means operatively connected to said source for feeding said fluid from said pilot valve to said source, and

. (4) another control member movable into (a) one position effective to close said second inlet means and to operatively connect said third outlet means to said four-th out- Ylet means, and

(b) two other positions effective to operatively connect respective ones of two sides of said actuating means to both said second inlet means and said fourth outlet means, and to operatively connect the respective other of said two sides of said actuating means to said fourth outlet means, and

(i) means, including said second inlet means, for feeding `said uid at a substantially constant rate of flow from said source to said pilot valve when said other control member is disposed in either of said two other positions thereof,

(j) `said first-mentioned control member having a passageway therethrough in position to connect said first inlet means to said `second outlet means when said first control member is disposed in said one position thereof, i

(k) said first-mentioned control member having (l) outwardly projecting spaced lands thereon,

and

(2) outwardly opening recesses disposed between respective pairs of said lands, and

(l) said lands and said recesses being disposed in such position that when said first-mentioned control member is disposed in said two other positions thereof respective ones of said recesses connect respective portions of said first outlet means to said first inlet means and said second outlet means, respectively,

(m) said lands having outwardly opening grooves therein, and interconnecting said grooves.

9. A hydraulic system comprising (a) control means for controlling the movement of awork load,

(b) a source of working fiuid,

(c) an elongated control valve for actuating said control means,

(d) said control valve including (1) first inlet means operatively connected to said source for receiving said fluid from said source,

(2) first outlet means operatively connected to said control means for feeding said fluid between said first outlet means and said control means,

(3) second outlet means operatively connected to said source for feeding said fluid from said control valve to said source, and

(4) a control member movable into (a) one position effective to operatively connect said first inlet means to said second outlet means, and to close said first outlet means, and

(b) two other positions effective to operatively connect respective ones of two sides of said control means to said first inlet means and the respective other of said two sides to said second outlet means,

(e) means operatively connected to said .second outlet means, for maintaining a predetermined minimum back pressure at said second outlet means,

(f) actuating means operatively connected to said control member for'moving the latter into said positions,

(g) a pilot valve for controlling said actuating member,

(h) said pilot valve including (l) second inlet means operatively connected to said source for receiving said fluid from .said source,

(2) third outlet means for feeding said fluid between said actuating means and said pilot valve,

(3) fourth outlet means operatively connected to said source for feeding said fluid from said pilot valve to said source, and

(4) another control member movable into (a) one position effective to close said second inlet means and to operatively connect said third outlet means to said fourth outlet means, and

(b) two other positions effective to operatively connect respective ones of two sides of said actuating means to both said second inlet means and said fourth outlet means, and to operatively connect the respective other of said two sides of said actuating means to said fourth outlet means, and

(i) means, including said second inlet means, for feeding said fiuid at a substantially constant rate of flow from said source to said pilot valve when said other control member is disposed in either of said two other positions thereof,

(j) said rst-mentioned control member having a passageway therethrough in position to connect said first inlet means to said second outlet means when said first control member is disposed in said one position thereof,

(k) said first-mentioned control member having (l) outwardly projecting spaced lands thereon,

and

(2) outwardly `opening recesses disposed between respective pairs of said lands, and

(l) said lands and said recesses being disposed in such position that when said first-mentioned control member is disposed in said two other positions thereof respective ones of said recesses connect respective portions of said first outlet means to said first inlet means and said second outlet means, respectively,

(m) Isaid lands having outwardly opening grooves therein, and interconnecting said grooves,

(n) said first outlet means having two branches disposed on respective sides of said first inlet means in axially outwardly spaced relation thereto, and

(o) said second outlet means having two branches disposed on respective sides of said first outlet means in axially outwardly spaced relation thereto.

10. A hydraulic system comprising (a) control means for controlling the movement of a 'work load,

(b) a source of working fiuid,

(c) a control valve for -actuating said control means,

(d) said control valve including (1) first inlet means operatively connected to said source for receiving said tiuid from said source, (2) first outlet means operatively connected to said control means for feeding said uid between said first outlet means and said control means, (3) second outlet means operatively connected to said source for feeding said fluid from said control valve to said source, and (4) a control member movable into (a) one position effective to operatively connect said first inlet means to said second outlet means, and t-o close said `first outlet means, and (b) two other positions effective to operatively connect respective ones of two sides of said control means to said first inlet means and the respective other of said two sides to said second outlet means,

(e) means operatively connected to said second outlet means, for maintaining -a predetermined minimum back pressure at said second outlet means,

(f) actuating means operatively connected to said control member for moving the latter into said positions,

(g) a pilot valve for controlling said lactuating member,

1(h) said pilot valve including (l) second inlet means operatively connected t-o said source for receiving said uid from said source,

(2) third outlet means for feeding said fluid between said actuating means and said pilot valve,

(3) fourth outlet means operatively connected to said source for feeding said fluid from said pilot v-alve to said source, and

`(4) another control member movable into (a) one position effective to close said second inlet means and to operatively connect said third outlet means to said fourth outlet means, and

(b) two other positions effective to operatively connect respective ones of two sides of said actuating means to both said second inlet means and said fourth outlet means, and to operatively connect the respective other of said two sides of said actuating means to said fourth outlet means, and

(i) means, including said second inlet means, for feeding said fluid at a substantially constant rate of flow from said source to said pilot valve when said other control member is disposed in either of said two other positions thereof,

(j) wherein (1) said other control member (a) is a substantially straight elongated member, and

(b) has three lands axially spaced thereon to afford a recess between each adjacent pair of lands,

(2) each of said recesses is connected to a respective one of said two sides of said actuating means in both of said two other positions of said other control member,

(3) one of said recesses is connected to said fourth outlet means, and the other of said recesses is connected to said fourth outlet means and said second inlet means when said -other control member is disposed in one of said two other positions-thereof, and

(4) said one recess is connected to said fourth outlet means and said second inlet means, and said other recess is connected to said fourth outlet means, when said other control member is disposed in the other of said two other positions thereof.

11. A hydraulic system comprising (a) control means for controlling the movement of a work load,

(b) a source of working uid,

(c) a control valve for actuating said control means,

(d) said control valve including (1) first inlet means operatively connected to said source for receiving said Huid from said source,

(2) first outlet means operatively connected to said control means for feeding said fluid bet-Ween said first outlet means and said control means,

(3) second outlet means operatively connected to said source for feeding said fluid from said control valve to said source, and

(4) a control member movable into (a) one position effective to operatively connect said first inlet means to said second outlet means, and to close said rst outlet means, and

(b) two other positions effective to operatively connect respective ones of two sides of said control means to said first inlet means and the respective -other of said two Isides to said second outlet means,

(e) means operatively connected to said second outlet means, for maintaining a predetermined minimum back pressure at said second outlet means,

(f) actuating means operatively connected to said control member for moving the latter into said positions,

(g) a pilot valve for controlling said actuating member,

(h) said pilot valve including (1) second inlet means operatively connected to said source for receiving said fluid from said source,

(2) third outlet means for feeding said uid between said actuating means and said pilot valve,

(3) fourth outlet means operatively connected to said source for feeding said uid from said pilot valve to said source, and

(4) another control member movable into (a) one position effective to close said second inlet means and to operatively connect said third outlet means to said fourth outlet means, and

(b) two other positions effective to operatively connect `respective ones of two sides of said actuating means to both said second inlet means and said fourth outlet means, and to -operatively connect the respective other of said two sides of said actuating means to said fourth outlet means, and

(i) means, including said second inlet means, for feeding said fluid at a substantially constant rate of flow from said source to said pilot valve when said other control member is disposed in either of said two other positions thereof,

(j) wherein (1) said other control member (a) is a substantially straight elongated member, and

(b) has three lands axially spaced thereon to afford a recess between each adjacent pair `of lands,

(2) each of said recesses is connected to a respective one of said two sides of said actuating means in both of said two other positions of said other control member,

(3) one of said recesses is connected to said fourth outlet means, and the other of said recesses is connected to said fourth outlet means and said second inlet means when said other control member is disposed in one of said two other positions thereof, and

(4) said one recess is connected to said fourth outlet means and said second inlet means and said other recess is connected to said fourth outlet means, when said other control member is disposed inthe other of said two other positions thereof,

(k) said lands being tapered in such position as to progressively open said second inlet means and progressively close said fourth outlet means as said other control member moves into either one of said two other positions.

References Cited by the Examiner UNITED STATES PATENTS 1,964,196 6/1934 Cuttat 91-448 2,172,981 9/1939 Maglott 91-461 2,375,255 5/1945' Snader et Ial 91-38 X 2,453,309 11/1948- Douglas 91-461 2,655,903 10/1953 Tyler 91-466 2,803,110 8/1957 Chittenden 91-304 2,969,808 1/1961 Harlacher 137-625.63

FOREIGN PATENTS 1,087,768 3/ 1953 Germany.

373,732 6/ 1932 Great Britain.

SAMUEL LEVINE, Primary Examiner.

FRED E. ENGELTHALER, Examiner. 

11. A HYDRAULIC SYSTEM COMPRISING (A) A CONTROL MEANS FOR CONTROLLING THE MOVEMENT OF A WORK LOAD, (B) A SOURCE OF WORKING FLUID, (C) A CONTROL VALVE FOR ACTUATING SAID CONTROL MEANS, (D) SAID CONTROL VALVE INCLUDING (1) FIRST INLET MEANS OPERATIVELY CONNECTED TO SAID SOURCE FOR RECEIVING SAID FLUID FROM SAID SOURCE, (2) FIRST OUTLET MEANS OPERATIVELY CONNECTED TO SAID CONTROL MEANS FOR FEEDING SAID FLUID BETWEEN SAID FIRST OUTLET MEANS AND SAID CONTROL MEANS (3) SECOND OUTLET MEANS OPERATIVELY CONNECTED TO SAID SOURCE FOR FEEDING SAID FLUID FROM SAID CONTROL VALVE TO SAID SOURCE, AND (4) A CONTROL MEMBER MOVABLE INTO (A'') ONE POSITION EFFECTIVE TO OERATIVELY CONNECT SAID FIRST INLET MEANS TO SAID SECOND OUTLET MEANS, AND TO CLOSE SAID FIRST OUTLET MEANS, AND (B'') TWO OTHER POSITIONS EFFECTIVE TO OPERATIVELY CONNECT RESPECTIVE ONES OF TWO SIDES OF SAID CONTROL MEANS TO SAID FIRST INLET MEANS AND THE RESPECTIVE OTHER OF SAID TWO SIDES TO SAID SECOND OUTLET MEANS, (E) MEANS OPERATIVELY CONNECTED TO SAID SECOND OUTLET MEANS, FOR MAINTAINING A PREDETERMINED MINIMUM BACK PRESSURE AT SAID SECOND OUTLET MEANS, (F) ACTUATING MEANS OPERATIVELY CONNECTED TO SAID CONTROL MEMBER FOR MOVING THE LATTER INTO SAID POSITIONS, (G) A PILOT VALVE FOR CONTROLLING SAID ACTUATING MEMBER, (H) SAID PILOT VALVE INCLUDING (1) SECOND INLET MEANS OPERATIVELY CONNECTED TO SAID SOURCE FOR RECEIVING SAID FLUID FROM SAID SOURCE, (2) THIRD OUTLET MEANS FOR FEEDING SAID FLUID BETWEEN SAID ACTUATING MEANS AND SAID PILOT VALVE, (3) FOURTH OUTLET MEANS OPERATIVELY CONNECTED TO SAID SOURCE FOR FEEDING SAID FLUID FROM SAID PILOT VALVE TO SAID SOURCE, AND (4) ANOTHER CONTROL MEMBER MOVABLE INTO (A'') ONE POSITION EFFECTIVE TO CLOSE SAID SECOND INLET MEANS AND TO OPERATIVELY CONNECT SAID THIRD OUTLET MEANS TO SAID FOURTH OUTLET MEANS, AND (B'') TWO OTHER POSITIONS EFFECTIVE TO OPERATIVELIY CONNECT RESPECTIVE ONES OF TWO SIDES OF SAID ACTUATING MEANS TO BOTH SAID SECOND INLET MEANS AND SAID FOURTH OUTLET MEANS, AND TO OPERATIVELY CONNECT THE RESPECTIVE OTHER OF SAID TWO SIDES OF SAID ACTUATING MEANS TO SAID FOURTH OUTLET MEANS, AND (I) MEANS, INCLUDING SAID SECOND INLET MEANS, FOR FEEDING SAID FLUID AT A SUBSTANTIALLY CONSTANT RATE OF FLOW FROM SAID SOURCE TO SAID PILOT VALVE WHEN SAID OTHER CONTROL MEMBER IS DISPOSED IN EITHER OF SAID TWO OTHER POSITIONS THEREOF, (J) WHEREIN (1) SAID OTHER CONTROL MEMBER (A'') IS A SUBSTANTIALLY STRAIGHT ELONGATED MEMBER, AND (B'') HAS THREE LANDS AXIALLY SPACED THEREON TO AFFORD A RECESS BETWEEN EACH ADJACENT PAIR OF LANDS, (2) EACH OF SAID RECESSES IS CONNECTED TO A RESPECTIVE ONE OF SAID TWO SIDES OF SAID ACTUATING MEANS IN BOTH SAID TWO OTHER POSITIONS OF SAID OTHER CONTROL MEMBER, (3) ONE OF SAID RECESSES IS CONNECTED TO SAID FOURTH OUTLET MEANS, AND THE OTHER OF SAID RECESSES IS CONNECTED TO SAID FOURTH OUTLET MEANS AND SAID SECOND INLET MEANS WHEN SAID OTHER CONTROL MEMBER IS DISPOSED IN ONE OF SAID TWO OTHER POSITIONS THEREOF, AND (4) SAID ONE RECESS IS CONNECTED TO SAID FOURTH OUTLET MEANS AND SAID SECOND INLET MEANS AND SAID OTHER RECESS IS CONNECTED TO SAID FOURTH OUTLET MEANS, WHEN SAID OTHER CONTROL MEMBER IS DISPOSED IN THE OTHER OF SAID TWO OTHER POSITIONS THEREOF, (K) SAID LANDS BEING TAPERED IN SUCH POSITION AS TO PROGRESSIVELY OPEN SAID SECOND INLET MEANS AND PROGRESSIVELY CLOSE SAID FOURTH OUTLET MEANS AS SAID OTHER CONTROL MEMBER MOVES INTO EITHER ONE OF SAID TWO OTHER POSITIONS. 